Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University...

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Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations

University of Cape Town 2008

Philip Lah

Collaborators:

Michael Pracy (ANU)

Frank Briggs (ANU)

Jayaram Chengalur (NCRA)

Matthew Colless (AAO)

Roberto De Propris (CTIO)

Talk OutlineIntroduction• Galaxies and Galaxy Evolution • HI 21cm emission & the HI coadding technique

Current Observations with the HI coadding technique• HI in star forming galaxies at z = 0.24 • HI in Abell 370, a galaxy cluster at z = 0.37

Future Observations with SKA pathfinders• using ASKAP and WiggleZ• using MeerKAT and zCOSMOS

What is HI?

The many lives of hydrogen

HI = neutral atomic hydrogen gas (one proton, one electron)

HII = ionised hydrogen gas (one proton) – chemistry H+

H2 = hydrogen molecular gas

What is HI?

The many lives of hydrogen

HI = neutral atomic hydrogen gas (one proton, one electron)

HII = ionised hydrogen gas (one proton) – chemistry H+

H2 = hydrogen molecular gas

The Significance of HI gas

HI Gas and Star Formation

Neutral atomic hydrogen gas

cloud (HI)

molecular gas cloud (H

star formation

Galaxy Types

Late-Type GalaxiesSpiral Irregular

Usually blue in optical colour

Early-Type GalaxiesElliptical Lenticular (S0)

Usually red in optical colour

Late-Type Galaxy Spectrum

optical spectrum of a

late-type galaxy

Wavelength (Å)

4000 5000 6000 7000

NGC 1832

[OII]Hβ

Hδ [OIII][SII]

Early-Type Galaxy Spectrum

line from Doyle &

Drinkwater 2006

Wavelength (Å)

4000 5000 6000 7000

NGC 1832

[OII]Hβ

Hδ [OIII][SII] optical

spectrum of an

early-type galaxy

Wavelength (Å)

4000 5000 6000 7000

NGC 1832

Ca H & K

G band

Late-Type Galaxy HI 21-cm Spectrum

NGC 5701 nearly face-on spiral galaxy

Early-Type Galaxies

Little or no neutral atomic hydrogen gas

As a consequence little or no active star formation

Evolution in Galaxies

Galaxy Clusters

Galaxy Cluster: Coma

Butcher-Oemler Effect

The Cosmic Star Formation Rate

Density

SFRD vs z

Hopkins 2004

SFRD vs time

Hopkins 2004

The Cosmic

Neutral GasDensity

The Cosmic Gas Density vs. Redshift

Zwaan et al. 2005HIPASSHI 21cm

Rao et al.2006DLAs

from MgII absorption

Prochaskaet al. 2005

Rao et al.2006DLAs

Lyman-α Absorption Systems

quasar

hydrogen gas clouds

Lyman-α emission

Lyman-α absorption by clouds

Wavelength

observer

Damped Lyman-α

Lyman-α 1216 Å rest frame

Wavelength (Å)4200 4400 4600 4800 5000 5200

Lyα emission

QSO 1425+6039 redshift z = 3.2 Keck HIRES optical spectrum

DLALyman-α forest

Rao et al.2006DLAs

HI 21-cm Emission

Neutral atomic hydrogen creates 21 cm radiation

proton electron

photon

HI 21cm emission

HI 21 cm emission decay half life ~10 million years (31014 s)

• 1 M 2.0 1033g 1.2 1057 atoms of hydrogen atoms

• total HI gas in galaxies ~ 107 to 1010 M

• HI 21 cm luminosity of ~2 1032 to 2 1035 ergs s-1

For comparison, in star forming galaxies:

• luminosity of H emission ~3 1039 to 3 1042 ergs s-1

HI 21 cm emission ~107 times less power than H emission

HI 21cm emission

HI 21cm Emission at

High Redshift

HI 21cm emission at z > 0.1

Telescope Redshift Obs Time

Number and HI Mass of galaxies

Who and When

WSRT z = 0.18 Abell 2218

200 hours 1 galaxy 4.8 109 M

Zwaan et al. 2001

VLA z = 0.19 Abell 2192

~80 hours 1 galaxy 7.0 109 M

Verheijen et al. 2004

WSRT two clusters at z = 0.19 &

z = 0.21420 hours

42 galaxies5109 to 41010 M

Verheijen et al. 2007

Arecibo z = 0.17 to 0.25

2 to 6 hours per

galaxy

26 galaxies(2 to 6) 1010 M

Catinella et al. 2007

Coadding HI signals

Radio Data Cube

Frequen

HI red

Coadding HI signals

Radio Data Cube

Frequen

HI red

positions of optical galaxies

Coadding HI signals

frequency

Coadding HI signals

frequency

Coadding HI signals

frequency

z3 velocity

HI signal

Current Observations -HI coadding

Giant Metrewave Radio Telescope

Anglo-Australian Telescope

multi-object, fibre fedspectrograph

2dF/AAOmega instrument

The Fujita galaxies H emission galaxies at z = 0.24

The Subaru Telescope

The Surprime-cam filters

H atz = 0.24

Late-Type Galaxy Spectrum

optical spectrum of a

late-type galaxy

Wavelength (Å)

4000 5000 6000 7000

NGC 1832

[OII]Hβ

Hδ [OIII][SII]

Intensity

Narrowband Filter: Hα detection

at z=0.24AAOmega Spectrum

optical red wavelengths

The Fujita Galaxies

Subaru Field 24’ × 30’

narrow band imaging Hα emission at z = 0.24

(Fujita et al. 2003, ApJL, 586, L115)

348 Fujita galaxies

121 redshifts using AAT

GMRT ~48 hours on field

SFRD vs z - Fujita

Hopkins 2004

Fujita et al. 2003

Fujita galaxies - B filter

Thumbnails 10’’ sq

Ordered by H

luminosity

Fujita galaxies - B filter

Thumbnails 10’’ sq

Ordered by H

luminosity

Coadded HI

Spectrum

HI spectrum all

Fujita galaxies neutral hydrogen gas measurement

using 121 redshifts - weighted average

MHI = (2.26 ± 0.90) ×109 M

binned

The Cosmic

Neutral GasDensity

my new point

Cosmic Neutral Gas Density vs. Time

Galaxy HI mass vs

Star Formation Rate

Galaxy HI Mass vs Star Formation Rate

HIPASS&

IRASdataz ~ 0

Doyle & Drinkwater

HI Mass vs Star Formation Rate at z = 0.24

line from Doyle &

Drinkwater 2006

all 121 galaxies

HI Mass vs Star Formation Rate at z = 0.24

line from Doyle &

Drinkwater 2006

42 bright L(Hα)

galaxies

42 medium L(Hα)

galaxies

37 faint L(Hα)

galaxies

Abell 370 a galaxy cluster at z = 0.37

Nearby Galaxy Clusters are Deficient in HI Gas

HI Deficiency in ClustersDefHI =

log(MHI exp. / MHI obs)

DefHI = 1 is 10% of expected HI gas

expected gas estimate based on optical diameter

and Hubble type

interactions between galaxies and interactions

with the inter-cluster medium removes the gas

from galaxies

Gavazzi et al. 2006

Why target moderate redshift clusters?

• at moderate redshifts the whole of the galaxy cluster core and its outskirts are within the field of view of a radio telescope (nearby this not the case – one has to target individual galaxies in clusters one by one)

• around a cluster there are many more galaxies that lie within a single telescope pointing than for a typical field

• the Butcher-Oemler effect – the increase in the blue fraction of galaxies in cluster cores with redshift – Is there an increase in the gas content as well?

Abell 370, a galaxy cluster at z = 0.37

large galaxy cluster of

order same size as

optical imaging ANU

40 inch telescope

spectroscopic follow-

up with the AAT

GMRT ~34 hours on

cluster

Abell 370 galaxy cluster

324 galaxies

105 blue (B-V 0.57)

219 red (B-V > 0.57)

Abell 370 galaxy cluster

Abell 370 galaxy clusterAbell 370 galaxy cluster

3σ extent of X-ray gas

R200 radius at which cluster

200 times denser than the

general field

The Problem of Galaxy Sizes and the GMRT

Galaxy Sizes

• GMRT has long baselines between dishes (up to 26 km)

• provides high resolution (~3 arcsec) so that the galaxies are

resolved – i.e. they are not point sources

• for coadding the HI signal I want the galaxies to be

unresolved as I can not see the size of individual galaxies

• for the Fujita galaxies I used an estimate of the HI size from

the optical properties of spiral and irregular field galaxies and

then smoothed radio data – i.e. make the galaxies unresolved

Galaxy Sizes

Complication

The Abell 370 galaxies are a mixture of early and late types

in a variety of environments.

My solution make multiple measurements of the HI gas

content of the coadded galaxies using a variety of

resolutions

Complication

The Abell 370 galaxies are a mixture of early and late types

in a variety of environments.

My solution is to make multiple measurements of the HI gas

content of the coadded galaxies using a

variety of resolutions

HI mass324 galaxies

219 galaxies

105 galaxies

94 galaxies

168 galaxies

156 galaxies

110 galaxies

214 galaxies

HI mass324 galaxies

219 galaxies

105 galaxies

94 galaxies

168 galaxies

156 galaxies

110 galaxies

214 galaxies

HI mass324 galaxies

219 galaxies

105 galaxies

94 galaxies

168 galaxies

156 galaxies

110 galaxies

214 galaxies

HI mass324 galaxies

219 galaxies

105 galaxies

94 galaxies

168 galaxies

156 galaxies

110 galaxies

214 galaxies

HI mass324 galaxies

219 galaxies

105 galaxies

94 galaxies

168 galaxies

156 galaxies

110 galaxies

214 galaxies

HI all spectrumall Abell 370 galaxies

neutral hydrogen gas measurement

using 324 redshifts – large smoothing

MHI = (6.6 ± 3.5) ×109 M

HI blue outside x-ray gasblue galaxies

outside of x-ray gas measurement of neutral hydrogen

gas content

using 94 redshifts – large smoothing

MHI = (23.0 ± 7.7) ×109 M

Comparisons with the

Literature

Average HI Mass Comparisons with

Abell 370 and Coma Comparison

214 galaxies

324 galaxies

110 galaxies

214 galaxies

324 galaxies

110 galaxies

214 galaxies

324 galaxies

110 galaxies

HI Density Comparisons

HI density field

HI density - inner regions of clusters

within 2.5 Mpc of cluster centers

HI Mass to Light Ratios

HI mass to optical B band luminosity for

Abell 370 galaxies

Uppsala General Catalog

Local Super Cluster

(Roberts & Haynes 1994)

HI Mass to Light Ratios

HI mass to optical B band luminosity for

Abell 370 galaxies

Uppsala General Catalog

Local Super Cluster

(Roberts & Haynes 1994)

Galaxy HI mass vs

Star Formation Rate

Galaxy HI Mass vs Star Formation Rate

HIPASS&

IRASdataz ~ 0

Doyle & Drinkwater

HI Mass vs Star Formation Rate in Abell 370

all 168 [OII]

emission galaxies

line from Doyle &

Drinkwater 2006

Average

HI Mass vs Star Formation Rate in Abell 370

81 blue [OII]

emission galaxies

line from Doyle &

Drinkwater 200687 red [OII]

emission galaxies

Average

Future Observations -HI coadding with SKA Pathfinders

SKA – Square Kilometer Array

• final site decision by 2012?? – money will be the deciding factor

• both South Africa and Australia are building SKA pathfinder telescopes to strengthen their case for site selection – telescopes also do interesting science

• SKA promises both high sensitivity with wide field of view

• possible SKA sites – South Africa and Australia

Why South Africa

and Australia?

Global Population Density

Population Density – South Africa

Population Density – Australia

Radio Interference

108 109

Frequency (Hz)

Radio Interference

108 109

Frequency (Hz)

HI at z = 0.4

HI at z = 1.0

The SKA pathfinders

MeerKAT

South African SKA pathfinder

ASKAP and MeerKAT parametersASKAP MeerKAT

Number of Dishes 45 80

Dish Diameter 12 m 12 m

Aperture Efficiency 0.8 0.8

System Temp. 35 K 30 K

Frequency range 700 – 1800 MHz 500 – 2500 MHz

Instantaneous bandwidth 300 MHz 512 MHz

Field of View:

at 1420 MHz (z = 0)

at 700 MHz (z = 1)

30 deg2

1.2 deg2

4.8 deg2

Maximum Baseline Length 8 km 10 km

Field of View:

at 1420 MHz (z = 0)

at 700 MHz (z = 1)

30 deg2

1.2 deg2

4.8 deg2

Field of View:

at 1420 MHz (z = 0)

at 700 MHz (z = 1)

30 deg2

1.2 deg2

4.8 deg2

z = 0.4 to 1.0 in a single observation

z = 0.2 to 1.0 in a single observation

single pointing assumes no evolution

in the HI mass function

(Johnston et al. 2007)

z = 0.45 to 1.0

980 MHz to 700 MHz

one year observations (8760 hours)

Simulated ASKAP HI detections

MeerKAT HI direct detections

• MeerKAT will detect galaxies in less time than ASKAP – due to its

higher sensitivity by ~2 times – it will still take a long time to detect

galaxies at z = 1.0 - perhaps in around a quarter of a year

• however at a particular redshift in a single pointing, MeerKAT will

end up with fewer total detections – due to MeerKAT`s smaller field of

• MeerKAT has a larger instantaneous bandwidth of 512 MHz – observe

from z = 0.2 to z = 1.0 in single observation (1200 MHz to 700 MHz)

• MeerKAT’s field of view is better matched to many current optical and

other wavelength surveys

What I could do with

the SKA pathfinders

using optical coadding of HI

if you gave them to me

TODAY.

WiggleZ and zCOSMOSWiggleZ zCOSMOS

Instrument/Telescope AAOmega on the AAT VIMOS on the VLT

Target Selectionultraviolet using the

GALEX satelliteoptical I band

IAB < 22.5

Survey Area1000 deg2 total

7 fields minimum size of ~100 deg2

COSMOS fieldsingle field

~2 deg2

Primary Redshift Range

0.5 < z < 1.0 0.1 < z < 1.2

Survey Timeline 2006 to 2009 2005 to 2008

nz by survey end 176,000 20,000

nz in March 2008 ~62,000 ~10,000

IAB < 22.5

~2 deg2

0.5 < z < 1.0 0.1 < z < 1.2

nz in March 2008 ~62,000 ~10,000

IAB < 22.5

~2 deg2

0.5 < z < 1.0 0.1 < z < 1.2

nz in March 2008 ~62,000 ~10,000

WiggleZ and

WiggleZ field

data as of July 2008 z = 0.45 to 1.0

ASKAP beam size

Diameter 6.2 degreesArea 30 deg2

square ~10 degrees across

ASKAP & WiggleZ 100hrs

nz = 5072

zCOSMOS and

MeerKAT

zCOSMOS field

data as of March 2008 z = 0.2 to 1.0

7118 galaxies

MeerKAT beam size at

1420 MHz z = 0

MeerKAT beam size at

1000 MHz z = 0.4

square ~1.3 degrees across

MeerKAT & zCOSMOS 100hrs

nz = 3559

half the number of

redshift

nz = 3559

HI Science with SKA Pathfinders

at High z

HI Science with SKA Pathfinders at High z

• provide constraints on the HI mass function with redshift (the

distribution of galaxies with HI mass) – won’t get information

on smaller HI systems – need SKA for that

• begin to trace how gas content varies in different

environments with redshift

• test star formation rate – HI correlation in the period of

extreme star formation activity in the universe

• won’t get galaxy velocity field information – again need SKA

Conclusion

• one can use coadding with optical redshifts to make measurement of

the HI 21 cm emission from galaxies at redshifts z > 0.1

• using this method we have measured the cosmic neutral gas density at

z = 0.24 and have shown that the value is consistent with that from

damped Lyα measurements

• galaxy cluster Abell 370 at z = 0.37 has significantly more gas than

similar clusters at z ~ 0

• the SKA pathfinders ASKAP and MeerKAT can measure HI 21 cm

emission from galaxies out to z = 1.0 using the coadding technique with

existing optical redshift surveys

Conclusion

Neutral Hydrogen Gas in Galaxies at Moderate Redshifts: Current and Future Observations University...

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